A multilayer substrate core structure (MPWB) may be conventionally fabricated by first providing a copper clad core. The copper clad core (CCL) may be a laminate that is copper clad on one or two sides depending on application needs. An example of such a fabrication process is shown in FIGS. 1-8. As seen in FIG. 1, a two sided CCL 101 is first provided including an insulating laminate 12 and top and bottom copper films 140 and 160, respectively. As seen in FIG. 2, the top and bottom copper films 140 and 160 are pre-patterned according to pre-determined interconnect patterns to be provided onto the laminate 120: such as by way of etching, to provide patterned copper films 150 and 170. Thereafter, as seen in FIG. 3, dielectric layer, such as ABF layers 190 and 210 (Ajinomoto Build-Up Film), are laminated onto the patterned copper films 150 and 160, and, as seen in FIG. 4 to provide a first intermediate laminate 180. As seen in FIG. 4, the first intermediate laminate 180 is then provided with through holes 201 by way of mechanical drilling and des-mearing to provide a second intermediate laminate 220. The de-smearing involves using a desmear solution to process the board to dissolve and remove any smears caused by drilling. As seen in FIG. 5, the through-holes 201 and the top and bottom surfaces of the intermediate laminate 220 are then plated to provide a plated intermediate laminate 240 with plated through holes 260. As seen in FIG. 6, the plated intermediate laminate 240 may be subjected thereafter to PTH plugging with a conductive material 250 such as copper to yield a plugged intermediate laminate 280. In a next stage, as shown in FIG. 7, the plugged intermediate laminate 280 may be lid plated with a conductive material such as copper to provide lids 270 and 290 on a top and bottom surface thereof the plating occurring on the top and bottom plating existing on laminate 280 of FIG. 6 to yield a lid plated intermediate laminate 300. Thereafter, the copper existing at the top and bottom surfaces of lid plated intermediate laminate 30 is patterned, such as by way of etching, to yield the wiring board 320 as shown in FIG. 8.
Prior art substrate are typically built on the base of a thick core (for example one having a thickness of about 0.7 mm (not including any build-up or conductive layers). The prior art core build up process can be lengthy. Taking a four layer core as an example, the macro process stages of a prior art fabrication process may include all of, core baking and cleaning, core copper patterning, copper roughening, ABF lamination, plated through hole drilling desmear, copper plating, copper roughening, plated through hole plugging, surface flattening, copper plating, and finally, copper patterning. However, mechanical plated through hole drilling can be the most expensive single process in the fabrication of a prior art multilayer substrate core structure. The need for plugging as explained above can add more to the manufacturing costs according to the prior art.
Disadvantageously, substrate core structures for substrate core structures according to the prior art can be costly, and can carry high manufacturing costs as a result of the use of mechanical drilling technology. These costs can skyrocket where the substrate core structures are miniaturized and scaled for future applications. In addition mechanical drilling is not suitable for producing holes smaller than about 150 microns.
The prior art fails to provide a cost-effective, expedient and reliable method of providing a multilayer substrate core structure.
For simplicity and clarity of illustration, elements in the drawings have not necessarily been drawn to scale. For example the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Where considered appropriate, reference numerals have been repeated among the drawings to indicate corresponding or analogous elements.